At times, it is necessary to remove water, ice and other sediment from gasoline before it is burned in an internal combustion engine. Alcohol blended gasolines tend to absorb water, and under certain conditions the amount absorbed can become great enough that it will begin to separate from the gasoline. Deicers such as isopropyl alcohol help to minimize this problem, but the concentration of water which may accumulate in some of the new gasoline blends may exceed the amount deicers can effectively dissolve.
Sediment traps have been used in the past between the fuel pump and the carburetor to remove unwanted impurities. Such traps do not remove impurities introduced at the carburetor, however.
Variable-venturi carburetors are widely used in snowmobiles and similar vehicles. Such carburetors typically include a piston which variably occludes an air passage, serving as a throttle valve. A main jet fixed to a lower portion of a float bowl in the carburetor includes a needle jet having a needle carried at the bottom of the piston. The main jet opens to a fuel reservoir which is either part of or connected to the float chamber. During engine operation, fuel in the fuel reservoir is drawn into the main jet and metered in the gap between the needle and the needle jet. The fuel is mixed with air and passes into the combustion chamber of the engine.
Under certain conditions, particularly in snowmobiles and other smaller engines used in cold weather, water can condense in the carburetor and then feeeze into ice particles which may block or restrict the fuel jets. This blockage can cause poor engine performance and stalling. Furthermore, for engines that depend on an oil/fuel mixture for lubrication, a clogged jet may have catastrophic effects on the engine due to lack of lubrication.